INTRODUCTORY ESSAY. 107 Flora predominates throughout the drier regions of the Hima- laya*. Siberian forms are, however, by no means confined to the drier, parts of the jchain, but may be observed even in the most humid regions of the Himalaya, and occasionally even on the mountains of tropical India. Thus Artemisia and Astragalus, which are perhaps the most characteristic genera of the Siberian type of vegetation, are not only abundant throughout Tibet and the interior Himalaya, but are repre- sented by a few species in the plains of the Panjab, on the outer slopes of the western Himalaya, and even on the Khasia mountains. Spir&a Kamtchatica, chamadrifolia, and sorbi- folia, and Paris polyphylla, are. also Siberian forms which extend into the rainy Himalaya; and Corydalis Sibirica and Nympkaa puyiila are remarkable instances of specific identity between Khasia and Siberian plants t- 5. The European type.—The extent to which European plants abound in India has never hitherto been even approxi- mately appreciated. Dr. Royle was the first to indicate this affinity between the vegetation of the eastern and western continents of the old world; and throughout his writings we find constant evidence of his never having lost sight of this being a marked feature. Had the collections, upon which he founded his conclusions, been critically compared and worked out, the keystone to the whole system of distribution in Western Asia coUd not have escaped him, which does not rest so much upon a number of. representative species, as * As a few instances, besides the many Rawuncuta<!e& and Iktmariaceirs enu- merated in the pages of the present volume, we may mention Tauscheria, de- sertoruw, JBiebersteinia odora, Fokentilla Salessovii, mttltifida, and lifn<rcat Cham&rJtodQS $abu<lo$a> Pyrus laccata^ Astragalus contortupJirat^ densi- florwt, aiiii jHtbitltt&uSt /Vwtv* friffhlff, Oxytropis diffbsa, Cicer Soongariam, iSWioft tivadrifldwn, Artemisia I>rm uuMtlus, sooparia^ Tournefortlana^ fases* and talsafM&t, tfatutMtova IxHfolia and fflffmrea, Mutyedium Tatari- Osmotfiamntftt Jlrapraiw (RkoiMe»drQ» anthop^on9 Bon), Salts awgw- ttluf baha/m/era, Carex meroglochin^ eteu&ptynay $bi/sodes* supine, and tristis* f It i» t^uious to remark that there are in Siberia a certain number of forms indicative of tropical Indian types, afy for instance, Mm&permm and Anandrict.